Means for preventing the rolling of ships.



H. FRAHM.

MEANS FOR PREVENTING THE ROLLING 0F SHIPS.

APPLICATION FILED JULY 15, 1908.

968,927. Patented Aug. 30,1910.

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UNITED STATES PATENT omuon.

HERMANN FRAHM, 0F HAMBURG, GERMANY.

MEANS FOR PREVENTING THE ROLLING OF SHIPS.

T 0 all whom it may concern:

Be it known that I, ll ERMANN FRAi-IM, a citizen of the free town ofHamburg, and resident of 1S Kloster Allee, of the free town of Hamburg,in the German Empire, engineer, have invented certain new and usefulImprovements in Means for Preventing the Rolling of Ships,.of which thefollowing is a specification:

This invention relates to means used for damping the rolling motion ofships by employing water tanks therein in which the periodic motion ofthe water when the ship rolls is utilized to counteract the rolling ofthe ship.

It has already been proposed to counteract the rolling of ships byproviding a double hull arranged so that the two walls of the hull wereat a greater distance apartat the bottom of the ship than at the sides.The outer hull was at the bottom provided with holes so as to place thespace between thehulls in communication with the outer water. ith thisconstruction the bulk of the water is arranged at the bottom of the shipand its action as regards damping the rolling motion is more in thenature of a heavy keel. I The result of this is that the rolling motionis not very efiiciently damped but merely the period of oscillation ofthe ship lengthened.

According to the present invention I propose to employ tanks arranged atthe sides of-the ship and connected to the outer water by pipes ofsmaller cross section than the tanks themselves. The cross section ofthe connection pipes is so dimensioned as to cause the periodic motionof the water in and out of the said tanks during rolling of the ship tocorrespond as nearly as possible with the calculated periodic motion ofthe ship during rolling, assuming that the pressures above the water inthe tanks on both sides of the vessel are maintained equal,-

for instance by constantly exposing the water in the tanks on both.sides to atmospheric pressure or in the case" of closed tanks byproviding for instance a cross connection between the top of the tanks.The

construction which I preferably employ conable means being provided formaintaining.

Specification of Letters Patent.

Application filed July 15, 1908.

Patented Aug. 30, 1910. Serial No. 443,597.

equal pressure above the water in opposite chambers for instance by apipe connecting the upper ends of the chamber. In practice however owingto the well known fact that each vessel develops an unforeseen rollingmotion peculiar to itself and owing to the constantly varying conditionsunder which a vessel travels, it is found desirable to provide means forVarying the lag in the flow of water in the tanks or chambers. Thisvariation may be obtained either by throttling more or less the flow ofwater through the connection to the sea or by varying the flow of airbetween the spaces above the water levels in the opposite tanks orchambers For special purposes it is sometimes necessary to get the waterlevels in both tanks into a different height in relation to the outersea. A suitable device for this is to control the degree of pressure orvacuum above the Water levels in the chambers and a simple method is toconnect the cross air pipe with a pressure or vacuum pipe.

The invention will be more readily understood from the followingdescription of the apparatus illustrated in the accompanying drawingwhich is a diagrammatic cross section through a ship provided withantirolling chambers according to the present invention.

In the drawing the chambers m and n on each side of the ship areconnected by pipes at and r respectively with the water in which thevessel is floating. The chambers are shown as provided with taperingsides which has the effect of enabling the period of the oscillations tobe regulated in a manner de scribed in a co-pending patent application,filed by me. The opemng to the sea Water is also tapered at s to preventshocksor undue friction. The upper ends of the vessels m and n areconnected by means of a pipe 0 in which a valve 0 is arranged to effectthrottling to control to some extent the pe-' riod of oscillation of thewater in and out of the chambers m and n. As can be seen from the figurethe outer water is higher than the water in the vessels during the nor-4 mal position of the ship and in consequence the air in the vessels mand n is in thls-case subjected to an initial pressure equal to the headof water 72. It will also be seen that in this case the quantities ofwater are alternately greater on each side during-rolling of the boat.During rolling the transference of the bulk of the weight from one sideof the boat to the other takes place periodically out of phase with therolling of the boat.

There are thus two periodic motions seta ainst one another and thereby abalancinge ect is obtained.

I claim 1: Apparatus for damping the rolling motion of ships havingwithln the ship, a

vertical chamber at each side of the ship, said chambers being widenedupwardly and connections from the bottom end of each of said chambers tothe sea Water, said chambers and connections being so dimensioned thatthe periodic oscillations of Water in and bers to the sea water, saidconnections and chambers being so pro ortioned that the period ofoscillation of t e water in and out of the chambers is substantiallyequal to the.

natural period of oscillation of the ship, and means for regulating thedegree of vacuum or pressure in the upper ends of said verticalchambers.

3. Apparatus for damping the rolling motion of ships having within theship, a

vertical chamber at each side of the ship, said chambers being closed attheir upper ends, connections from each of said chambers to the seawater, said connections and the chambers being so proportioned that theperiod ofoscillation of the water in and out of the chambers issubstantially equal to the natural period of oscillation of the ship, apipe joining the upper ends of the vertical chambers on each side'of theship and a valve in said pipe.

4. Apparatus for damping the rolling motion of ships having within theship a vertical chamber at each side of the ship, said chambers beingwidened upwardly and closed at their upper ends, connections from thebottom end of each of said chambers to the sea water, said chambers andconnections being so dimensioned that the period of oscillation of waterin and out of said vertical chambers is substantially equal to thenatural period of oscillation of the ship, a pipe joining the upper endsof the vertical chambers at each side of the ship and a valve in saidpipe.

In witness whereof I have hereunto set my hand in the presence of twowitnesses.

HERMANN FRAHM.

Witnesses ERNEST H. L. MUMMENHOFF, O'r'ro W. HELLMRICH.

